Shared blockchain data storage based on error correction code

ABSTRACT

Disclosed herein are methods, systems, and apparatus, including computer programs encoded on computer storage media, for communicating and sharing blockchain data. One of the methods includes determining historic state data associated with one or more blocks created prior to a current block on a blockchain; performing error correction coding of the historic state data to generate encoded historic state data; dividing, based on one or more predetermined rules, the encoded historic state data into a plurality of data sets; selecting one or more data sets from the plurality of data sets based on the one or more predetermined rules; hashing the one or more data sets to generate one or more hash values corresponding to the one or more data sets; storing the one or more hash values; and deleting, by the blockchain node, the one or more data sets.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No. 16/712,702 filed on Dec. 12, 2019, which is a continuation of PCT Application No. PCT/CN2019/098913, filed on Aug. 1, 2019, and each application is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

This specification relates to shared storage of blockchain data based on error correction code.

BACKGROUND

Distributed ledger systems (DLSs), which can also be referred to as consensus networks, and/or blockchain networks, enable participating entities to securely and immutably store data. DLSs are commonly referred to as blockchain networks without referencing any particular user case. Examples of types of blockchain networks can include public blockchain networks, private blockchain networks, and consortium blockchain networks. A consortium blockchain network is provided for a select group of entities, which control the consensus process, and includes an access control layer.

Blockchain-based programs can be executed by a distributed computing platform such as an Ethereum. For example, the Ethereum virtual machine (EVM) provides the runtime environment for smart contracts in Ethereum. An Ethereum blockchain can be viewed as a transaction-based state machine. State data in an Ethereum can be assembled to a global shared-state referred to as a world state. The world state comprises a mapping between Ethereum account addresses and account states. The world state can be stored in data structures such as the Merkle Patricia tree (MPT).

Besides state data, blockchain networks can also store other types of data such as block data and index data. Block data can include block header and block body. The block header can include identity information of a particular block and the block body can include transactions that are confirmed with the block. When more and more transactions are entered into the blockchain, state data and block data can grow very large in size. In some DLSs, every node stores an entire copy of the blockchain, which can take large amount of storage space, even if some of the old block data or state data are not frequently visited. In some DLSs, a few shared nodes store the entire copy of the blockchain and share blockchain data with other blockchain nodes which can create “data inequality.”

Accordingly, it would be desirable to reduce the amount of data stored on the nodes in the DLS while maintaining data equality and data processing efficiency.

SUMMARY

This specification describes technologies for communicating and sharing blockchain data. These technologies generally involve determining, by a blockchain node, historic state data associated with one or more blocks created prior to a current block on a blockchain; performing, by the blockchain node, error correction coding of the historic state data to generate one or more encoded historic state data; dividing, by the blockchain node based on one or more predetermined rules, the encoded historic state data to a plurality of data sets; selecting, by the blockchain node, one or more data sets from the plurality of data sets based on the one or more predetermined rules; hashing, by the blockchain node, the one or more data sets to generate one or more hash values corresponding to the one or more data sets; storing, by the blockchain node, the one or more hash values; and deleting, by the blockchain node, the one or more data sets.

This specification also provides one or more non-transitory computer-readable storage media coupled to one or more processors and having instructions stored thereon which, when executed by the one or more processors, cause the one or more processors to perform operations in accordance with embodiments of the methods provided herein.

This specification further provides a system for implementing the methods provided herein. The system includes one or more processors, and a computer-readable storage medium coupled to the one or more processors having instructions stored thereon which, when executed by the one or more processors, cause the one or more processors to perform operations in accordance with embodiments of the methods provided herein.

It is appreciated that methods in accordance with this specification may include any combination of the aspects and features described herein. That is, methods in accordance with this specification are not limited to the combinations of aspects and features specifically described herein, but also include any combination of the aspects and features provided.

The details of one or more embodiments of this specification are set forth in the accompanying drawings and the description below. Other features and advantages of this specification will be apparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an example of an environment that can be used to execute embodiments of this specification.

FIG. 2 depicts an example of an architecture in accordance with embodiments of this specification.

FIG. 3 depicts an example of a fixed depth Merkle tree (FDMT) data structure in accordance with embodiments of this specification.

FIG. 4 depicts examples of databases for storing blockchain data in accordance with embodiments of this specification.

FIG. 5 depicts an example of a state data encoding and hashing process in accordance with embodiments of this specification.

FIG. 6 depicts an example of a data storage arrangement in accordance with embodiments of this specification.

FIG. 7 depicts an example of a process that can be executed in accordance with embodiments of this specification.

FIG. 8 depicts examples of modules of an apparatus in accordance with embodiments of this specification.

Like reference numbers and designations in the various drawings indicate like elements.

DETAILED DESCRIPTION

This specification describes technologies for communicating and sharing blockchain data. These technologies generally involve determining, by a blockchain node, historic state data associated with one or more blocks created prior to a current block on a blockchain; performing, by the blockchain node, error correction coding of the historic state data to generate one or more encoded historic state data; dividing, by the blockchain node based on one or more predetermined rules, the encoded historic state data to a plurality of data sets; selecting, by the blockchain node, one or more data sets from the plurality of data sets based on the one or more predetermined rules; hashing, by the blockchain node, the one or more data sets to generate one or more hash values corresponding to the one or more data sets; storing, by the blockchain node, the one or more hash values; and deleting, by the blockchain node, the one or more data sets.

The techniques described in this specification produce several technical effects. For example, embodiments of the subject matter can allow savings of storage resources of blockchain nodes without significantly sacrificing computational efficiency. Because most data in the historic state tree are “cold” data that are infrequently used, by saving only a portion of ECC encoded historic state data and sharing the rest of the encoded data with other blockchain nodes, storage space consumption across the blockchain network can be reduced.

In some embodiments, instead of storing the entire historic state tree, a blockchain node can store a selected portion of the ECC encoded historic state data and hash values corresponding to the rest of the encoded historic state data. To retrieve unsaved state data from other blockchain nodes, the blockchain node can send corresponding hash values to the other blockchain nodes that store the encoded historic state data. Since hash values are irreversible, the blockchain node can easily verify whether the received data are authentic, by comparing the corresponding hash values to the locally stored copies. As such, data security can be ensured and faulty nodes can be easily identified and reported. Even if the blockchain node receives unauthentic data from faulty blockchain nodes, the historic state data can be recovered as long as the percentage of the unauthentic data is less than or equal to the maximum fraction of erroneous bits or of missing bits allowed by the ECC.

To provide further context for embodiments of this specification, and as introduced above, distributed ledger systems (DLSs), which can also be referred to as consensus networks (e.g., made up of peer-to-peer nodes), and blockchain networks, enable participating entities to securely, and immutably conduct transactions, and store data. Although the term blockchain is generally associated with particular networks, and/or use cases, blockchain is used herein to generally refer to a DLS without reference to any particular use case.

A blockchain is a data structure that stores transactions in a way that the transactions are immutable. Thus, transactions recorded on a blockchain are reliable and trustworthy. A blockchain includes one or more blocks. Each block in the chain is linked to a previous block immediately before it in the chain by including a cryptographic hash of the previous block. Each block also includes a timestamp, its own cryptographic hash, and one or more transactions. The transactions, which have already been verified by the nodes of the blockchain network, are hashed and encoded into a Merkle tree. A Merkle tree is a data structure in which data at the leaf nodes of the tree is hashed, and all hashes in each branch of the tree are concatenated at the root of the branch. This process continues up the tree to the root of the entire tree, which stores a hash that is representative of all data in the tree. A hash purporting to be of a transaction stored in the tree can be quickly verified by determining whether it is consistent with the structure of the tree.

Whereas a blockchain is a decentralized or at least partially decentralized data structure for storing transactions, a blockchain network is a network of computing nodes that manage, update, and maintain one or more blockchains by broadcasting, verifying and validating transactions, etc. As introduced above, a blockchain network can be provided as a public blockchain network, a private blockchain network, or a consortium blockchain network. Embodiments of this specification are described in further detail herein with reference to a consortium blockchain network. It is contemplated, however, that embodiments of this specification can be realized in any appropriate type of blockchain network.

In general, a consortium blockchain network is private among the participating entities. In a consortium blockchain network, the consensus process is controlled by an authorized set of nodes, which can be referred to as consensus nodes, one or more consensus nodes being operated by a respective entity (e.g., a financial institution, insurance company). For example, a consortium of ten (10) entities (e.g., financial institutions, insurance companies) can operate a consortium blockchain network, each of which operates at least one node in the consortium blockchain network.

In some examples, within a consortium blockchain network, a global blockchain is provided as a blockchain that is replicated across all nodes. That is, all consensus nodes are in perfect state consensus with respect to the global blockchain. To achieve consensus (e.g., agreement to the addition of a block to a blockchain), a consensus protocol is implemented within the consortium blockchain network. For example, the consortium blockchain network can implement a practical Byzantine fault tolerance (PBFT) consensus, described in further detail below.

FIG. 1 is a diagram illustrating an example of an environment 100 that can be used to execute embodiments of this specification. In some examples, the environment 100 enables entities to participate in a consortium blockchain network 102. The environment 100 includes computing devices 106, 108, and a network 110. In some examples, the network 110 includes a local area network (LAN), wide area network (WAN), the Internet, or a combination thereof, and connects web sites, user devices (e.g., computing devices), and back-end systems. In some examples, the network 110 can be accessed over a wired and/or a wireless communications link. In some examples, the network 110 enables communication with, and within the consortium blockchain network 102. In general, the network 110 represents one or more communication networks. In some cases, the computing devices 106, 108 can be nodes of a cloud computing system (not shown), or each computing device 106, 108 can be a separate cloud computing system including a number of computers interconnected by a network and functioning as a distributed processing system.

In the depicted example, the computing systems 106, 108 can each include any appropriate computing system that enables participation as a node in the consortium blockchain network 102. Examples of computing devices include, without limitation, a server, a desktop computer, a laptop computer, a tablet computing device, and a smartphone. In some examples, the computing systems 106, 108 host one or more computer-implemented services for interacting with the consortium blockchain network 102. For example, the computing system 106 can host computer-implemented services of a first entity (e.g., user A), such as a transaction management system that the first entity uses to manage its transactions with one or more other entities (e.g., other users). The computing system 108 can host computer-implemented services of a second entity (e.g., user B), such as a transaction management system that the second entity uses to manage its transactions with one or more other entities (e.g., other users). In the example of FIG. 1, the consortium blockchain network 102 is represented as a peer-to-peer network of nodes, and the computing systems 106, 108 provide nodes of the first entity, and second entity respectively, which participate in the consortium blockchain network 102.

FIG. 2 depicts an example of an architecture 200 in accordance with embodiments of this specification. The example conceptual architecture 200 includes participant systems 202, 204, 206 that correspond to Participant A, Participant B, and Participant C, respectively. Each participant (e.g., user, enterprise) participates in a blockchain network 212 provided as a peer-to-peer network including a plurality of nodes 214, at least some of which immutably record information in a blockchain 216. Although a single blockchain 216 is schematically depicted within the blockchain network 212, multiple copies of the blockchain 216 are provided, and are maintained across the blockchain network 212, as described in further detail herein.

In the depicted example, each participant system 202, 204, 206 is provided by, or on behalf of Participant A, Participant B, and Participant C, respectively, and functions as a respective node 214 within the blockchain network. As used herein, a node generally refers to an individual system (e.g., computer, server) that is connected to the blockchain network 212, and enables a respective participant to participate in the blockchain network. In the example of FIG. 2, a participant corresponds to each node 214. It is contemplated, however, that a participant can operate multiple nodes 214 within the blockchain network 212, and/or multiple participants can share a node 214. In some examples, the participant systems 202, 204, 206 communicate with, or through the blockchain network 212 using a protocol (e.g., hypertext transfer protocol secure (HTTPS)), and/or using remote procedure calls (RPCs).

Nodes 214 can have varying degrees of participation within the blockchain network 212. For example, some nodes 214 can participate in the consensus process (e.g., as miner nodes that add blocks to the blockchain 216), while other nodes 214 do not participate in the consensus process. As another example, some nodes 214 store a complete copy of the blockchain 216, while other nodes 214 only store copies of portions of the blockchain 216. For example, data access privileges can limit the blockchain data that a respective participant stores within its respective system. In the example of FIG. 2, the participant systems 202, 204, and 206 store respective, complete copies 216′, 216″, and 216′″ of the blockchain 216.

A blockchain (e.g., the blockchain 216 of FIG. 2) is made up of a chain of blocks, each block storing data. Examples of data include transaction data representative of a transaction between two or more participants. While transactions are used herein by way of non-limiting example, it is contemplated that any appropriate data can be stored in a blockchain (e.g., documents, images, videos, audio). Examples of a transaction can include, without limitation, exchanges of something of value (e.g., assets, products, services, currency). The transaction data is immutably stored within the blockchain. That is, the transaction data cannot be changed.

Before storing in a block, the transaction data is hashed. Hashing is a process of transforming the transaction data (provided as string data) into a fixed-length hash value (also provided as string data). It is not possible to un-hash the hash value to obtain the transaction data. Hashing ensures that even a slight change in the transaction data results in a completely different hash value. Further, and as noted above, the hash value is of fixed length. That is, no matter the size of the transaction data the length of the hash value is fixed. Hashing includes processing the transaction data through a hash function to generate the hash value. An example of a hash function includes, without limitation, the secure hash algorithm (SHA)-256, which outputs 256-bit hash values.

Transaction data of multiple transactions are hashed and stored in a block. For example, hash values of two transactions are provided, and are themselves hashed to provide another hash. This process is repeated until, for all transactions to be stored in a block, a single hash value is provided. This hash value is referred to as a Merkle root hash, and is stored in a header of the block. A change in any of the transactions will result in change in its hash value, and ultimately, a change in the Merkle root hash.

Blocks are added to the blockchain through a consensus protocol. Multiple nodes within the blockchain network participate in the consensus protocol, and perform work to have a block added to the blockchain. Such nodes are referred to as consensus nodes. PBFT, introduced above, is used as a non-limiting example of a consensus protocol. The consensus nodes execute the consensus protocol to add transactions to the blockchain, and update the overall state of the blockchain network.

In further detail, the consensus node generates a block header, hashes all of the transactions in the block, and combines the hash value in pairs to generate further hash values until a single hash value is provided for all transactions in the block (the Merkle root hash). This hash is added to the block header. The consensus node also determines the hash value of the most recent block in the blockchain (i.e., the last block added to the blockchain). The consensus node also adds a nonce value, and a timestamp to the block header.

In general, PBFT provides a practical Byzantine state machine replication that tolerates Byzantine faults (e.g., malfunctioning nodes, malicious nodes). This is achieved in PBFT by assuming that faults will occur (e.g., assuming the existence of independent node failures, and/or manipulated messages sent by consensus nodes). In PBFT, the consensus nodes are provided in a sequence that includes a primary consensus node, and backup consensus nodes. The primary consensus node is periodically changed. Transactions are added to the blockchain by all consensus nodes within the blockchain network reaching an agreement as to the world state of the blockchain network. In this process, messages are transmitted between consensus nodes, and each consensus nodes proves that a message is received from a specified peer node, and verifies that the message was not modified during transmission.

In PBFT, the consensus protocol is provided in multiple phases with all consensus nodes beginning in the same state. To begin, a client sends a request to the primary consensus node to invoke a service operation (e.g., execute a transaction within the blockchain network). In response to receiving the request, the primary consensus node multicasts the request to the backup consensus nodes. The backup consensus nodes execute the request, and each sends a reply to the client. The client waits until a threshold number of replies are received. In some examples, the client waits for f+1 replies to be received, where f is the maximum number of faulty consensus nodes that can be tolerated within the blockchain network. The final result is that a sufficient number of consensus nodes come to an agreement on the order of the record that is to be added to the blockchain, and the record is either accepted, or rejected.

In some blockchain networks, cryptography is implemented to maintain privacy of transactions. For example, if two nodes want to keep a transaction private, such that other nodes in the blockchain network cannot discern details of the transaction, the nodes can encrypt the transaction data. An example of cryptography includes, without limitation, symmetric encryption, and asymmetric encryption. Symmetric encryption refers to an encryption process that uses a single key for both encryption (generating ciphertext from plaintext), and decryption (generating plaintext from ciphertext). In symmetric encryption, the same key is available to multiple nodes, so each node can en-/de-crypt transaction data.

Asymmetric encryption uses keys pairs that each include a private key, and a public key, the private key being known only to a respective node, and the public key being known to any or all other nodes in the blockchain network. A node can use the public key of another node to encrypt data, and the encrypted data can be decrypted using other node's private key. For example, and referring again to FIG. 2, Participant A can use Participant B′s public key to encrypt data, and send the encrypted data to Participant B. Participant B can use its private key to decrypt the encrypted data (ciphertext) and extract the original data (plaintext). Messages encrypted with a node's public key can only be decrypted using the node's private key.

Asymmetric encryption is used to provide digital signatures, which enables participants in a transaction to confirm other participants in the transaction, as well as the validity of the transaction. For example, a node can digitally sign a message, and another node can confirm that the message was sent by the node based on the digital signature of Participant A. Digital signatures can also be used to ensure that messages are not tampered with in transit. For example, and again referencing FIG. 2, Participant A is to send a message to Participant B. Participant A generates a hash of the message, and then, using its private key, encrypts the hash to provide a digital signature as the encrypted hash. Participant A appends the digital signature to the message, and sends the message with digital signature to Participant B. Participant B decrypts the digital signature using the public key of Participant A, and extracts the hash. Participant B hashes the message and compares the hashes. If the hashes are same, Participant B can confirm that the message was indeed from Participant A, and was not tampered with.

As described earlier, blockchain networks can store different types of data such as state data, block data, and index data. State data are often stored as a content-addressed state tree (e.g., MPT or FDMT). Content-addressed state trees are incremental in nature. That is, changes of account states are reflected by adding new tree structures instead of only updating values of the existing state tree. Therefore, the content-addressed state trees can grow very large in size when blocks are continuously added to the blockchain. On the other hand, most data in the trees are infrequently used historic state data. Storing all historic state data in every consensus node can be quite inefficient in terms of storage resource usage.

Under the FDMT storage scheme, state data can be separated into current state data associated with the current block and historic state data associated with all blocks of the blockchain. To save on storage resources without materially affecting computational efficiency, it would be desirable that each consensus node in the blockchain network stores only a portion of the historic state data and retrieves the rest of the historic state data from other nodes to reduce storage consumption. However, if faulty nodes or unreliable nodes exist in the blockchain network, the received historic state data may not be trusted or data loss may occur.

In some embodiments, ECC such as erasure code can be used to encode the historic state data. By sharing ECC encoded historic state data instead of the original historic state data, even if unauthentic data exists or data loss occurs, the original historic state data can be recovered, as long as the unauthentic data or data loss is less than or equal to the maximum fraction of erroneous bits or of missing bits that can be corrected by the ECC.

FIG. 3 depicts an example of an FDMT data structure 300 in accordance with embodiments of this specification. Under FDMT, account states can be stored as key value pairs (KVPs) in the structures of a historic state tree 302 and a current state tree 304. The keys correspond to addresses that uniquely identify values of blockchain accounts. The historic state tree 302 can include an entire copy of available state information of the blockchain. The current state tree 304 can include state information of a current block. Therefore, the size of the current state tree 304 can be significantly smaller than the size of the historic state tree 302.

In some embodiments, the current state tree 304 can be a location-addressed state tree. For a location-addressed state tree, a node value of the current state tree 304 can be retrieved based on a key that uniquely identifies the node (i.e., a node ID). When new node is added to the current state tree 304, node value can be associated with its unique node ID (e.g., ID 1-1, ID 2-1, etc. of the current state tree 304) without regard to its content. In some cases, a KVP of the current state tree 304 can be expressed as <node ID, node value>. In some cases, the keys of the KVPs can further include a corresponding block ID of the node value. In such cases, the node ID can serve as prefix and the block ID can serve us suffix of keys. The KVP of the current state tree 304 can then be expressed as <node ID+block ID, node value>.

In some embodiments, the historic state tree 302 can be a content-addressed state tree. For a content-addressed state tree, each account value can have a content address uniquely associated with the value of the information content itself. To retrieve information from a historic state tree 302, a content identifier can be provided, from which the location of the account value can be determined and retrieved. Similar to MPT, each node of the historic state tree 302 can include a hash value of a pointer (e.g., Hash 1, Hash2, and Hash 3 under the historic state tree 302) pointing to the next node of the tree. Following paths of the pointers, the last elements stores hash values of end portion of the keys (e.g., Hash4, Hash5, Hash6, and Hash7 under the historic state tree 302) and the values that the keys are paired with. KVPs of the historic state tree 302 can be expressed as <hash(node value), node value>.

Since node addresses of content-addressed trees are dependent on node values, new state information can be added as additional tree structure to the historic state tree 302 rather than making changes to the existing tree to preserve original tree structure and improve data storage/retrieval efficiency.

FIG. 4 depicts examples of databases 400 for storing blockchain data in accordance with embodiments of this specification. The databases 400 can be key-value databases such as levelDB or RocksDB. The databases 400 can store data under the FDMT data structure, which includes history database 410 for storing historic state tree and current database 412 for storing current state tree. For the four blocks depicted in FIG. 4, block i−2 402, block i−1 404, and block i 406 are previously completed blocks. Block i+1 408 is a current block. Each block can have a block header and a block body. The block header can include information such as a root hash of the world state. The root hash can serve as a secure and unique identifier for the state trees. In other words, the root hash can be cryptographically dependent on account states. The block body can include confirmed transactions of the corresponding block.

The history database 410 can store historic state data as the historic state tree. Historic state data can be any state data associated with previous blocks of the blockchain. The current database 412 can store current state data as the current state tree (e.g., as depicted in box 412 of FIG. 4). Current state data can be state data associated with a current block. After the current block is created on the blockchain, a new block will be created and the current state data becomes historic state data. State data generated with the creation of the new block becomes the new current state data.

The historic state data and current state data can include historical and current account states. Ethereum blockchain accounts can include externally owned accounts and contract accounts. Externally owned accounts can be controlled by private keys and are not associated with any code for executing smart contract. Contract accounts can be controlled by their contract code are associated with code for executing smart contract.

States of Ethereum accounts can include four components: nonce, balance, codeHash, and storageRoot. If the account is an externally owned account, the nonce can represent the number of transactions sent from the account address. The balance can represent the digital assets owned by the account. The codeHash can be the hash of an empty string. The storageRoot can be empty. If the account is a contract account, the nonce can represent the number of contracts created by the account. The balance can represent the digital assets owned by the account. The codeHash can be the hash of a virtual machine code associated with the account. The storageRoot can store a root hash associated with a storage tree. The storage tree can store contract data by encoding the hash of the storage contents of the account.

The historic state tree can include an entire copy of account states of the blockchain from the genesis block, and can be updated according to transaction executions. For example, root hash stored in previous block i−1 404 is a root hash of the world state at the time block i−1 404 is completed. The world state is associated with all transactions stored in block i−1 404 and blocks prior to block i−1 404. Similarly, root hash stored in the current block i+1 408 is a root hash of the world state associated with all transactions stored in block i+1 408 and blocks prior to block i+1 408.

The current state tree can include state information that is updated or added due to transactions newly added to the current block i+1 408. As discussed in the description of FIG. 3, the historic state tree can store state information as KVPs expressed as <hash(node value), node value>, which is content-addressable. In some embodiments, the current state tree can be location-addressed based on one or more location related IDs. For example, the current state tree can store state information as KVPs expressed as <node ID, node value>, where the node values can be addressed based on their corresponding node IDs. As another example, the keys of the KVPs can be a combination of the node ID and the corresponding block ID of the node value. The node ID can serve as prefix and the block ID can serve us suffix of keys for traversing values of an FDMT or MPT.

As described above, under the FDMT data structure, current state data can be separated from the historic state data. In an Ethereum type system, state information associated with the current block can be considered as “hot” data, frequently retrieved by a virtual machine to execute smart contracts. Historic state data can be stored as a historic state tree, which can include an entire copy of account states of the blockchain from the genesis block. State information associated with previous blocks stored in the historic state tree can be considered as “cold” data, which are visited less often for executing smart contract.

Because data in a content-addressed state tree (e.g., MPT or the historic state) are incremental in nature, historic state tree can grow very large in size due to generations of new blocks. Because most data in the historic state tree are “cold” data that are infrequently used, storing those data in every blockchain node can be quite inefficient in terms of usage of storage resources.

To save on storage resources without significantly compromising computational efficiency, the historic state data can be encoded by ECC and shared among blockchain nodes in a blockchain network.

FIG. 5 depicts an example of a state data encoding and hashing process 500 in accordance with embodiments of this specification. In this example, a blockchain network of four blockchain nodes is depicted, which are blockchain nodes 502, 504, 506, and 508. Using blockchain node 502 as an example to illustrate the encoding and hashing process 500, the blockchain node 502 can store block data of the blockchain network to block body of a block 512. In the illustrated example, after block data are stored in a block (i.e., block 100), the blockchain node 502 can engage in a consensus process with other blockchain nodes 502, 504, 506, and 508. During the consensus process, the blockchain node 502 can perform a consensus algorithm, such as proof of work (PoW) or proof of stake (PoS) to create a corresponding block on the blockchain.

After the block 100 is created on the blockchain, it changes from a current block to a historic block. The current state data (such as the current state data stored in the current database 412 as discussed in the description of FIG. 4) becomes historic state data to be added to the historic state tree. The blockchain node 502 can perform error-correction coding (ECC) 514 to the historic state data associated with block 100.

ECC can be used for controlling errors or losses of data over unreliable transmissions by adding redundant bits to the data. The redundancy can allow errors or losses of data to be corrected without retransmission of the data. One example ECC can be the erasure coding. Using the erasure coding, a message of k symbols can be encoded to a codeword with n symbols, where k and n are natural numbers, and k<n. The message can be recovered from a subset of the n-symbol codeword. The fraction r=k/n is the code rate of the erasure code.

By using ECC, each of the blockchain nodes can store a portion of the encoded historic state data and retrieve the rest of the encoded historic state data from other blockchain nodes when needed. In some cases, the ECC can be performed when utilization rate of computational resource of the blockchain node 502 is lower than a predetermined value (e.g., 40%). In such cases, the ECC may be performed to historic state data associated with more than one block, and the interference of ECC to other computational operations on the blockchain node 502 can be reduced. In some embodiments, ECC can be performed when the usage of storage space of the blockchain node 502 is greater than or equal to a predetermined percentage, such that after ECC, some portions of the encoded historic state data can be deleted to free up storage space.

Using again block 100 as an example, after performing ECC 514 to the historic state data, the ECC encoded data can be divided into a plurality of data sets based on one or more predetermined rules. In the illustrated example shown in FIG. 5, the encoded historic state data of block 100 is divided into four data sets, which are Data1, Data2, Data3, and VData1, each to be kept by one of the blockchain nodes 502, 504, 506, and 508. VData1 can represent the redundant bits of the ECC for error correction. Data1 is selected to be stored by the blockchain node 502 according to the one or more predetermined rules. Data2, Data3, and Vdata1 are selected to be separately hashed 516 to generate hash values Dhash2, Dhash3, and Vhash1, respectively.

Referring now to FIG. 6, FIG. 6 depicts an example of a data storage arrangement 600 in accordance with embodiments of this specification. As discussed earlier, Data1 is selected to be stored by the blockchain node 502 according to the one or more predetermined rules. Based on the data storage arrangement 600, blockchain node 504 stores Data2 and separately hashes Data1, Data3, and Vdata1 to generate hash values Dhash1, Dhash3, and Vhash1, respectively. Blockchain node 506 stores Data3 and separately hashes Data1, Data2, and Vdata1 to generate hash values Dhash, Dhash2 and Vhash1, respectively. Blockchain node 508 stores Vdata1 and separately hashes Data1, Data2, and Vdata3 to generate hash values Dhash1, Dhash2 and Dhash3, respectively.

Referring back to FIG. 5, since the hash values correspond to encoded data sets of one or more blocks, they can be indexed by corresponding block IDs of the one or more blocks. For example, the blockchain node 502 can index Data1, Dhash1, Dhash2, and Vhash1 associated with block 100 with a block ID 100. As such, the blockchain node 502 can use the indexed block ID(s) to map the hash values of the historic state data to their corresponding blocks.

It is to be understood that other data storage arrangements can be made for the blockchain nodes 502, 504, 506, and 508, according to the one or more predetermined rules. Generally, the one or more predetermined rules can include one or more instructions for dividing the encoded data to a plurality of data sets based on the number of blockchain nodes in a blockchain network. The one or more predetermined rules can also include assignments of one or more data sets of the plurality of data sets to be stored or hashed by each of the blockchain nodes. To ensure data equality, the one or more predetermined rules can include an assignment of at least one data set to be stored by each blockchain node of the blockchain network. In some examples, based on the predetermined rules, the encoded historic state data of block 100 can be divided to more than four datasets when the blockchain network has more than four nodes. In some examples, each blockchain node can store more than one data set and hash the rest of the data sets stored by other nodes.

After generating and storing Dhash2, Dhash3, and Vhash1, the blockchain node 502 can delete Data2, Data3, and Vdata1 from storage to save storage space. As such, for each block, the blockchain node 502 only stores one ECC encoded data set (i.e., Data1) and three hash values (i.e., Dhash2, Dhash3, and Vhash1), instead of the entire block. As such, storage space can be significantly reduced. Similar to block 100, the encoding and hashing process can be performed for historic state data corresponding to other blocks.

When the blockchain node 502 needs to retrieve historic state data, it can retrieve Data2, Data3, and Vdata1 from blockchain nodes 504, 506, and 508, respectively, according to the one or more predetermined rules. To retrieve data sets from other blockchain nodes 504, 506, and 508, blockchain node 502 can send hash values corresponding to the data sets to be retrieved according to the one or more predetermined rules.

For example, to retrieve Data2, the blockchain node 502 can send Dhash2 to the blockchain node 504. If the blockchain node 504 has Data2 stored, it can send the Data2 back to the blockchain node 502 in response to receiving the Dhash2. After receiving the Data2 from the blockchain node 504, the blockchain node 502 can hash the received data set and compare the hash value with Dhash2. If the hash value is the same as Dhash2, the blockchain node 502 can determine that the received data set is authentic. Otherwise, the received data set is determined to be unauthentic. The blockchain node 502 can report the blockchain node 504 as a faulty node (or a Byzantine node) when the received data set is determined as unauthentic. If the percentage of unauthentic data received by the blockchain node 502 is less than or equal to the maximum fraction of erroneous bits or of missing bits that can be corrected by the ECC, block 100 can be recovered from the locally stored and received data sets.

FIG. 7 is a flowchart of an example of a process 700 for communicating and sharing blockchain data. For convenience, the process 700 will be described as being performed by a system of one or more computers, located in one or more locations, and programmed appropriately in accordance with this specification. For example, a computing device in a computing system, e.g., the computing system 106, 108 of FIG. 1, appropriately programmed, can perform the process 700.

At 702, a blockchain node determines historic state data associated with one or more blocks created prior to a current block on a blockchain.

At 704, the blockchain node performs error correction coding of the historic state data to generate one or more encoded historic state data.

At 706, the blockchain node based on one or more predetermined rules divides the encoded historic state data to a plurality of data sets.

At 708, the blockchain node selects one or more data sets from the plurality of data sets based on the one or more predetermined rules.

At 710, the blockchain node hashes the one or more data sets to generate one or more hash values corresponding to the one or more data sets.

At 712, the blockchain node stores the one or more hash value.

At 714, the blockchain node deletes the one or more data sets.

In some cases, the error correction coding is performed when utilization rate of computational resource of the blockchain node is less than or equal to a predetermined value or usage of storage space of the blockchain node is greater than or equal to a predetermined percentage.

In some cases, the error correction coding is performed by adding redundant bits to the one or more blocks.

In some cases, the error correction coding is erasure coding.

In some cases, the blockchain node is a first blockchain node, and the process 700 further comprising: after deleting the one or more data sets, determining that the historic state data is associated with at least one of the one or more data sets deleted by the first blockchain node; identifying, based on the one or more predetermined rules, a second blockchain node that stores at least one of the one or more data sets and at least one hash value corresponding to the at least one of the one or more data sets; and sending the at least one hash value to the second blockchain node for retrieving the at least one of the one or more data sets.

In some cases, the at least one hash value is first at least one hash value, the process 700 further comprising: receiving, from the second blockchain node, at least one data set in response to sending the first at least one hash value; and hashing the at least one data set to generate second at least one hash value.

In some cases, the process 700 further comprising: determining that the at least one data set is authentic if the first at least one hash value is same as the second at least one hash value.

In some cases, the process 700 further comprising: identifying, based on the one or more predetermined rules, a third blockchain node that stores at least one of the one or more data sets and third at least one hash value corresponding to the at least one of the one or more data sets; sending the third at least one hash value to the third blockchain node for retrieving the at least one of the one or more data sets; receiving, from the third blockchain node, at least one data set in response to sending the third at least one hash value; hashing the at least one data set to generate fourth at least one hash value; and determining that the at least one data set is authentic if the third at least one hash value is same as the fourth at least one hash value.

In some cases, the process 700 further comprising: before the deleting the one or more data sets, indexing the one or more hash values with an identifier identifying the one or more blocks associated with the historic state data.

In some cases, the one or more predetermined rules include one or more instructions for dividing the encoded historic state data to the plurality of data sets based on a quantity of blockchain nodes of a blockchain network and assignments of one or more data sets of the plurality of data sets to be stored or hashed by each of the blockchain nodes.

FIG. 8 is a diagram of on example of modules of an apparatus 800 in accordance with embodiments of this specification.

The apparatus 800 can be an example of an embodiment of a blockchain node configured to communicate and share blockchain data. The apparatus 800 can correspond to the embodiments described above, and the apparatus 800 includes the following: a determining module 802 that determines historic state data associated with one or more blocks created prior to a current block on a blockchain; a performing module 804 that performs error correction coding of the historic state data to generate one or more encoded historic state data; a dividing module 806 that divides the encoded historic state data to a plurality of data sets; a selecting module 808 that selects one or more data sets from the plurality of data sets based on the one or more predetermined rules; a hashing module 810 that hashes the one or more data sets to generate one or more hash values corresponding to the one or more data sets; a storing module 812 that stores the one or more hash values; and a deleting module 814 that deletes the one or more data sets.

In an optional embodiment, the error correction coding is performed when utilization rate of computational resource of the blockchain node is less than or equal to a predetermined value or usage of storage space of the blockchain node is greater than or equal to a predetermined percentage.

In an optional embodiment, the error correction coding is performed by adding redundant bits to the one or more blocks. In an optional embodiment, the error correction coding is erasure coding.

In an optional embodiment, the blockchain node is a first blockchain node, and the apparatus 800 further comprising: a determining submodule that determines the historic state data is associated with at least one of the one or more data sets deleted by the first blockchain node; an identification submodule that identifies, based on the one or more predetermined rules, a second blockchain node that stores at least one of the one or more data sets and at least one hash value corresponding to the at least one of the one or more data sets; and a sending submodule that sends the at least one hash value to the second blockchain node for retrieving the at least one of the one or more data sets.

In an optional embodiment, the at least one hash value is first at least one hash value, the apparatus 800 further comprises: a receiving submodule that receives, from the second blockchain node, at least one data set in response to sending the first at least one hash value; and a hashing submodule that hashes the at least one data set to generate second at least one hash value.

In an optional embodiment, the apparatus 800 further comprising: a determination submodule that determines that the at least one data set is authentic if the first at least one hash value is same as the second at least one hash value.

In an optional embodiment, the apparatus 800 further comprising: an identification submodule that identifies, based on the one or more predetermined rules, a third blockchain node that stores at least one of the one or more data sets and third at least one hash value corresponding to the at least one of the one or more data sets; a sending submodule that sends the third at least one hash value to the third blockchain node for retrieving the at least one of the one or more data sets; a receiving submodule that receives, from the third blockchain node, at least one data set in response to sending the third at least one hash value; a hashing submodule that hashes the at least one data set to generate fourth at least one hash value; and a determining submodule that determines the at least one data set is authentic if the third at least one hash value is same as the fourth at least one hash value.

In an optional embodiment, the apparatus 800 further comprises: an indexing submodule that indexes the one or more hash values with an identifier identifying the one or more blocks associated with the historic state data.

In an optional embodiment, the one or more predetermined rules include one or more instructions for dividing the encoded historic state data to the plurality of data sets based on a quantity of blockchain nodes of a blockchain network and assignments of one or more data sets of the plurality of data sets to be stored or hashed by each of the blockchain nodes.

The system, apparatus, module, or unit illustrated in the previous embodiments can be implemented by using a computer chip or an entity, or can be implemented by using a product having a certain function. A typical embodiment device is a computer, and the computer can be a personal computer, a laptop computer, a cellular phone, a camera phone, a smartphone, a personal digital assistant, a media player, a navigation device, an email receiving and sending device, a game console, a tablet computer, a wearable device, or any combination of these devices.

For an embodiment process of functions and roles of each module in the apparatus, references can be made to an embodiment process of corresponding steps in the previous method. Details are omitted here for simplicity.

Because an apparatus embodiment basically corresponds to a method embodiment, for related parts, references can be made to related descriptions in the method embodiment. The previously described apparatus embodiment is merely an example. The modules described as separate parts may or may not be physically separate, and parts displayed as modules may or may not be physical modules, may be located in one position, or may be distributed on a number of network modules. Some or all of the modules can be selected based on actual demands to achieve the objectives of the solutions of the specification. A person of ordinary skill in the art can understand and implement the embodiments of the present application without creative efforts.

Referring again to FIG. 8, it can be interpreted as illustrating an internal functional module and a structure of a blockchain node. An execution body in essence can be an electronic device, and the electronic device includes the following: one or more processors; and one or more computer-readable memories configured to store an executable instruction of the one or more processors. In some embodiments, the one or more computer-readable memories are coupled to the one or more processors and have programming instructions stored thereon that are executable by the one or more processors to perform algorithms, methods, functions, processes, flows, and procedures, as described in this specification.

The techniques described in this specification produce several technical effects. For example, embodiments of the subject matter can allow savings of storage resources of blockchain nodes without significantly sacrificing computational efficiency. Because most data in the historic state tree are “cold” data that are infrequently used, by saving only a portion of ECC encoded historic state data and sharing the rest of the encoded data with other blockchain nodes, storage space consumption across the blockchain network can be reduced.

In some embodiments, instead of storing the entire historic state tree, a blockchain node can store a selected portion of the ECC encoded historic state data and hash values corresponding to the rest of the encoded historic state data. To retrieve unsaved state data from other blockchain nodes, the blockchain node can send corresponding hash values to the other blockchain nodes that store the encoded historic state data. Since hash values are irreversible, the blockchain node can easily verify whether the received data are authentic, by comparing the corresponding hash values to the locally stored copies. As such, data security can be ensured and faulty nodes can be easily identified and reported. Even if the blockchain node receives unauthentic data from faulty blockchain nodes, the historic state data can be recovered as long as the percentage of the unauthentic data is less than or equal to the maximum fraction of erroneous bits or of missing bits allowed by the ECC.

Described embodiments of the subject matter can include one or more features, alone or in combination.

For example, in a first embodiment, a computer-implemented method for communicating shared blockchain data, the method comprising: sending, by a blockchain node of a blockchain network, current state information and one or more transactions associated with a current block of a blockchain to one or more shared storage nodes of the blockchain network, wherein the blockchain node stores block header associated with every block of the blockchain and the current state information, the one or more shared storage nodes store block body and historic state information associated with every block of the blockchain, and wherein the historic state information is stored as key-value pairs (KVPs) of a historic state tree with values being account states of accounts associated with the blockchain network and keys being hash values of the corresponding account states; verifying, by the blockchain node, that the one or more transactions are stored by the one or more shared storage nodes; and receiving, by the blockchain node from one of the one or more shared storage nodes, a notification of a transaction associated with the blockchain node.

The foregoing and other described embodiments can each, optionally, include one or more of the following features:

A first feature, combinable with any of the following features, specifies that the error correction coding is performed when utilization rate of computational resource of the blockchain node is less than or equal to a predetermined value or usage of storage space of the blockchain node is greater than or equal to a predetermined percentage.

A second feature, combinable with any of the following features, specifies that the error correction coding is performed by adding redundant bits to the one or more blocks.

A third feature, combinable with any of the following features, specifies that the error correction coding is erasure coding.

A fourth feature, combinable with any of the following features, specifies that the blockchain node is a first blockchain node, and the method further comprising: after deleting the one or more data sets, determining that the historic state data is associated with at least one of the one or more data sets deleted by the first blockchain node; identifying, based on the one or more predetermined rules, a second blockchain node that stores at least one of the one or more data sets and at least one hash value corresponding to the at least one of the one or more data sets; and sending the at least one hash value to the second blockchain node for retrieving the at least one of the one or more data sets.

A fifth feature, combinable with any of the following features, specifies that the at least one hash value is first at least one hash value, the method further comprising: receiving, from the second blockchain node, at least one data set in response to sending the first at least one hash value; and hashing the at least one data set to generate second at least one hash value.

A sixth feature, combinable with any of the following features, specifies that the method further comprising: determining that the at least one data set is authentic if the first at least one hash value is same as the second at least one hash value.

A seventh feature, combinable with any of the following features, specifies that the method further comprising: identifying, based on the one or more predetermined rules, a third blockchain node that stores at least one of the one or more data sets and third at least one hash value corresponding to the at least one of the one or more data sets; sending the third at least one hash value to the third blockchain node for retrieving the at least one of the one or more data sets; receiving, from the third blockchain node, at least one data set in response to sending the third at least one hash value; hashing the at least one data set to generate fourth at least one hash value; and determining that the at least one data set is authentic if the third at least one hash value is same as the fourth at least one hash value.

An eighth feature, combinable with any of the following features, specifies that the method further comprising: before the deleting the one or more data sets, indexing the one or more hash values with an identifier identifying the one or more blocks associated with the historic state data.

A ninth feature, combinable with any of the following features, specifies that the one or more predetermined rules include one or more instructions for dividing the encoded historic state data to the plurality of data sets based on a quantity of blockchain nodes of a blockchain network and assignments of one or more data sets of the plurality of data sets to be stored or hashed by each of the blockchain nodes.

Embodiments of the subject matter and the actions and operations described in this specification can be implemented in digital electronic circuitry, in tangibly-embodied computer software or firmware, in computer hardware, including the structures disclosed in this specification and their structural equivalents, or in combinations of one or more of them. Embodiments of the subject matter described in this specification can be implemented as one or more computer programs, e.g., one or more modules of computer program instructions, encoded on a computer program carrier, for execution by, or to control the operation of, data processing apparatus. For example, a computer program carrier can include one or more computer-readable storage media that have instructions encoded or stored thereon. The carrier may be a tangible non-transitory computer-readable medium, such as a magnetic, magneto optical, or optical disk, a solid state drive, a random access memory (RAM), a read-only memory (ROM), or other types of media. Alternatively, or in addition, the carrier may be an artificially generated propagated signal, e.g., a machine-generated electrical, optical, or electromagnetic signal that is generated to encode information for transmission to suitable receiver apparatus for execution by a data processing apparatus. The computer storage medium can be or be part of a machine-readable storage device, a machine-readable storage substrate, a random or serial access memory device, or a combination of one or more of them. A computer storage medium is not a propagated signal.

A computer program, which may also be referred to or described as a program, software, a software application, an app, a module, a software module, an engine, a script, or code, can be written in any form of programming language, including compiled or interpreted languages, or declarative or procedural languages; and it can be deployed in any form, including as a stand-alone program or as a module, component, engine, subroutine, or other unit suitable for executing in a computing environment, which environment may include one or more computers interconnected by a data communication network in one or more locations.

A computer program may, but need not, correspond to a file in a file system. A computer program can be stored in a portion of a file that holds other programs or data, e.g., one or more scripts stored in a markup language document, in a single file dedicated to the program in question, or in multiple coordinated files, e.g., files that store one or more modules, sub programs, or portions of code.

Processors for execution of a computer program include, by way of example, both general- and special-purpose microprocessors, and any one or more processors of any kind of digital computer. Generally, a processor will receive the instructions of the computer program for execution as well as data from a non-transitory computer-readable medium coupled to the processor.

The term “data processing apparatus” encompasses all kinds of apparatuses, devices, and machines for processing data, including by way of example a programmable processor, a computer, or multiple processors or computers. Data processing apparatus can include special-purpose logic circuitry, e.g., an FPGA (field programmable gate array), an ASIC (application specific integrated circuit), or a GPU (graphics processing unit). The apparatus can also include, in addition to hardware, code that creates an execution environment for computer programs, e.g., code that constitutes processor firmware, a protocol stack, a database management system, an operating system, or a combination of one or more of them.

The processes and logic flows described in this specification can be performed by one or more computers or processors executing one or more computer programs to perform operations by operating on input data and generating output. The processes and logic flows can also be performed by special-purpose logic circuitry, e.g., an FPGA, an ASIC, or a GPU, or by a combination of special-purpose logic circuitry and one or more programmed computers.

Computers suitable for the execution of a computer program can be based on general or special-purpose microprocessors or both, or any other kind of central processing unit. Generally, a central processing unit will receive instructions and data from a read only memory or a random access memory or both. Elements of a computer can include a central processing unit for executing instructions and one or more memory devices for storing instructions and data. The central processing unit and the memory can be supplemented by, or incorporated in, special-purpose logic circuitry.

Generally, a computer will also include, or be operatively coupled to receive data from or transfer data to one or more storage devices. The storage devices can be, for example, magnetic, magneto optical, or optical disks, solid state drives, or any other type of non-transitory, computer-readable media. However, a computer need not have such devices. Thus, a computer may be coupled to one or more storage devices, such as, one or more memories, that are local and/or remote. For example, a computer can include one or more local memories that are integral components of the computer, or the computer can be coupled to one or more remote memories that are in a cloud network. Moreover, a computer can be embedded in another device, e.g., a mobile telephone, a personal digital assistant (PDA), a mobile audio or video player, a game console, a Global Positioning System (GPS) receiver, or a portable storage device, e.g., a universal serial bus (USB) flash drive, to name just a few.

Components can be “coupled to” each other by being commutatively such as electrically or optically connected to one another, either directly or via one or more intermediate components. Components can also be “coupled to” each other if one of the components is integrated into the other. For example, a storage component that is integrated into a processor (e.g., an L2 cache component) is “coupled to” the processor.

To provide for interaction with a user, embodiments of the subject matter described in this specification can be implemented on, or configured to communicate with, a computer having a display device, e.g., a LCD (liquid crystal display) monitor, for displaying information to the user, and an input device by which the user can provide input to the computer, e.g., a keyboard and a pointing device, e.g., a mouse, a trackball or touchpad. Other kinds of devices can be used to provide for interaction with a user as well; for example, feedback provided to the user can be any form of sensory feedback, e.g., visual feedback, auditory feedback, or tactile feedback; and input from the user can be received in any form, including acoustic, speech, or tactile input. In addition, a computer can interact with a user by sending documents to and receiving documents from a device that is used by the user; for example, by sending web pages to a web browser on a user's device in response to requests received from the web browser, or by interacting with an app running on a user device, e.g., a smartphone or electronic tablet. Also, a computer can interact with a user by sending text messages or other forms of message to a personal device, e.g., a smartphone that is running a messaging application, and receiving responsive messages from the user in return.

This specification uses the term “configured to” in connection with systems, apparatus, and computer program components. For a system of one or more computers to be configured to perform particular operations or actions means that the system has installed on it software, firmware, hardware, or a combination of them that in operation cause the system to perform the operations or actions. For one or more computer programs to be configured to perform particular operations or actions means that the one or more programs include instructions that, when executed by data processing apparatus, cause the apparatus to perform the operations or actions. For special-purpose logic circuitry to be configured to perform particular operations or actions means that the circuitry has electronic logic that performs the operations or actions.

While this specification contains many specific embodiment details, these should not be construed as limitations on the scope of what is being claimed, which is defined by the claims themselves, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in this specification in the context of separate embodiments can also be realized in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiments can also be realized in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially be claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claim may be directed to a subcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings and recited in the claims in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system modules and components in the embodiments described above should not be understood as requiring such separation in all embodiments, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products.

Particular embodiments of the subject matter have been described. Other embodiments are within the scope of the following claims. For example, the actions recited in the claims can be performed in a different order and still achieve desirable results. As one example, the processes depicted in the accompanying figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results. In some cases, multitasking and parallel processing may be advantageous. 

What is claimed is:
 1. A computer-implemented method for storing blockchain data, the computer-implemented method comprising: obtaining, by a first blockchain node, a first hash value corresponding to a first historic state data item; identifying, by the first blockchain node and based on one or more predetermined rules, a second blockchain node that stores at least a first encoded data item, wherein the first encoded data item is generated based on the first historic state data item and an error correction coding process; sending, by the first blockchain node, the first hash value to the second blockchain node for retrieving the first encoded data item; and in response to sending the first hash value to the second blockchain node, receiving, by the first blockchain node, the first encoded data item from the second blockchain node.
 2. The computer-implemented method of claim 1, wherein the error correction coding process is performed when utilization rate of computational resource of the second blockchain node is less than or equal to a predetermined value or usage of storage space of the second blockchain node is greater than or equal to a predetermined percentage.
 3. The computer-implemented method of claim 1, wherein the first historic state data item is associated with one or more blocks created prior to a current block on a blockchain, and wherein the error correction coding process is performed by adding redundant bits to the one or more blocks.
 4. The computer-implemented method of claim 1, wherein the error correction coding process is erasure coding.
 5. The computer-implemented method of claim 1, further comprising: deleting, by the first blockchain node, one or more data sets associated with the first historic state data item.
 6. The computer-implemented method of claim 5, wherein the first historic state data item is associated with one or more blocks created prior to a current block on a blockchain, and further comprising: before deleting, by the first blockchain node, the one or more data sets associated with the first historic state data item, indexing the first hash value with an identifier identifying the one or more blocks associated with the first historic state data item.
 7. The computer-implemented method of claim 1, further comprising: hashing, by the first blockchain node, the first encoded data item to generate a second hash value.
 8. The computer-implemented method of claim 7, further comprising: comparing, by the first blockchain node, the first hash value to the second hash value; determining, by the first blockchain node, that the first hash value is equal to the second hash value; and determining, by the first blockchain node, the first encoded data item is authentic based on determining that the first hash value is equal to the second hash value.
 9. The computer-implemented method of claim 1, further comprising: obtaining, by the first blockchain node, a third hash value corresponding to a second historic state data item; identifying, by the first blockchain node and based on the one or more predetermined rules, a third blockchain node that stores at least a second encoded data item, wherein the second encoded data item is generated based on the second historic state data item and the error correction coding process; sending, by the first blockchain node, the third hash value to the third blockchain node for retrieving the second encoded data item; in response to sending the third hash value to the third blockchain node, receiving, by the first blockchain node, the second encoded data item from the third blockchain node; hashing, by the first blockchain node, the second encoded data item to generate a fourth hash value; and determining that the second encoded data item is authentic if the third hash value is equal to the fourth hash value.
 10. The computer-implemented method of claim 1, wherein the one or more predetermined rules include one or more instructions for dividing historic state data into the first encoded data item based on a quantity of blockchain nodes of a blockchain network and an assignment of the first encoded data item to be stored or hashed by the second blockchain node.
 11. A non-transitory, computer-readable medium storing one or more instructions executable by a computer system to perform operations for storing blockchain data, comprising: obtaining, by a first blockchain node, a first hash value corresponding to a first historic state data item; identifying, by the first blockchain node and based on one or more predetermined rules, a second blockchain node that stores at least a first encoded data item, wherein the first encoded data item is generated based on the first historic state data item and an error correction coding process; sending, by the first blockchain node, the first hash value to the second blockchain node for retrieving the first encoded data item; and in response to sending the first hash value to the second blockchain node, receiving, by the first blockchain node, the first encoded data item from the second blockchain node.
 12. The non-transitory, computer-readable medium of claim 11, wherein the error correction coding process is performed when utilization rate of computational resource of the second blockchain node is less than or equal to a predetermined value or usage of storage space of the second blockchain node is greater than or equal to a predetermined percentage.
 13. The non-transitory, computer-readable medium of claim 11, further comprising: deleting, by the first blockchain node, one or more data sets associated with the first historic state data item.
 14. The non-transitory, computer-readable medium of claim 13, wherein the first historic state data item is associated with one or more blocks created prior to a current block on a blockchain, and further comprising: before deleting, by the first blockchain node, the one or more data sets associated with the first historic state data item, indexing the first hash value with an identifier identifying the one or more blocks associated with the first historic state data item.
 15. The non-transitory, computer-readable medium of claim 11, further comprising: obtaining, by the first blockchain node, a third hash value corresponding to a second historic state data item; identifying, by the first blockchain node and based on the one or more predetermined rules, a third blockchain node that stores at least a second encoded data item, wherein the second encoded data item is generated based on the second historic state data item and the error correction coding process; sending, by the first blockchain node, the third hash value to the third blockchain node for retrieving the second encoded data item; in response to sending the third hash value to the third blockchain node, receiving, by the first blockchain node, the second encoded data item from the third blockchain node; hashing, by the first blockchain node, the second encoded data item to generate a fourth hash value; and determining that the second encoded data item is authentic if the third hash value is equal to the fourth hash value.
 16. The non-transitory, computer-readable medium of claim 11, wherein the one or more predetermined rules include one or more instructions for dividing historic state data into the first encoded data item based on a quantity of blockchain nodes of a blockchain network and an assignment of the first encoded data item to be stored or hashed by the second blockchain node.
 17. A computer-implemented system for storing blockchain data, comprising: one or more processors; and one or more computer-readable memories coupled to the one or more processors and having instructions stored thereon that are executable by the one or more processors to perform one or more operations for: obtaining, by a first blockchain node, a first hash value corresponding to a first historic state data item; identifying, by the first blockchain node and based on one or more predetermined rules, a second blockchain node that stores at least a first encoded data item, wherein the first encoded data item is generated based on the first historic state data item and an error correction coding process; sending, by the first blockchain node, the first hash value to the second blockchain node for retrieving the first encoded data item; and in response to sending the first hash value to the second blockchain node, receiving, by the first blockchain node, the first encoded data item from the second blockchain node.
 18. The computer-implemented system of claim 17, wherein the error correction coding process is performed when utilization rate of computational resource of the second blockchain node is less than or equal to a predetermined value or usage of storage space of the second blockchain node is greater than or equal to a predetermined percentage.
 19. The computer-implemented system of claim 17, further comprising: deleting, by the first blockchain node, one or more data sets associated with the first historic state data item.
 20. The computer-implemented system of claim 17, wherein the one or more predetermined rules include one or more instructions for dividing historic state data into the first encoded data item based on a quantity of blockchain nodes of a blockchain network and an assignment of the first encoded data item to be stored or hashed by the second blockchain node. 